In the operation of railroads there is an ongoing need to replace defective running gear of the rail cars, running gear that has failed or is failing in service. In most trains there is usually present an average of three defective wheel sets. The presence of these defective sets may be determined aurally, by the squealing and grinding of the wheel flanges against the rails, by the thumping of tread flat spots on the rail; by visual inspection: and frequently by the operation of infra-red "hot-box" detectors.
Trains on the North American continent may operate with individual cars standard-coupled together, or the cars are semi-permanently coupled together in close-coupled sub-units such as five car, six car or ten car "packs", being typically referred to as a "five pack", a "six pack", etc., having semi-permanent coupling and service connections.
Present practice for the replacement of defective running gear requires the breaking down of the train to isolate the affected freight or passenger car, including, where necessary, the uncoupling of the semi-permanent connections to the defective car, so that it can be shunted no a car shop or service area, and the repair effected by substituting a serviced wheel set for the defective set, using an overhead lifting system to raise cars bodily from the affected wheel set. The tonal servicing process regularly requires as much as three days, largely to separate the effected cars; shunting them from the train and then shunting them, one at a time, to the car shop or service area, while a time of about three hours is required to carry out the actual replacement of each wheel replacement set, before the train can be reassembled, re-connected and returned to service. Meanwhile, the trainload of goods being transported is delayed, with possible spoilage, interrupted schedules, etc.
The separation of passenger rail cars is complicated by the frequent requirement to disconnect electric heating, door operation, etc. which are labour intensive and time consuming.
Three-level automobile carrier cars present yet more difficulties as they may not be lifted by cranes.
In the case of the modern practice of "critical path" supply of components, in industries such as the automotive industry, this type of delay is highly undesirable, and in many instances eliminates railroads from consideration as a potential carrier. Also, in the case of perishables, particularly fruit, the same applies, with reliance consequently being vested in the aircraft and trucking industries.
The delay presently involved in changing a defective wheel set is so adverse to effective train service that the decision to remedy the defect may be postponed, and a safety hazard occurs, with possible tragic consequences.
The present method of servicing individual rail cars within car shops typically relies upon the use of a trolley having a heavy duty mechanical lift, extending far beneath the trolley, into an elongated deep well extending the length of the service pit.
The lift has a ram housed in an elongated tubular housing suspended beneath the servicing trolley, the tube extending several feet below the trolley and its tracks, and being accommodated within a deep well, located in the bottom of the service pit, and extending along its length. This well most usually contains accumulated garbage, and frequently becomes filled with ground-water, ice or other water. The service pit enables the lateral transfer of a disabled truck or wheel set clear of the car, for replacement by a serviced set, using a crane or other lifting equipment to substitute the serviced set for the defective unit upon the servicing trolley.
Various aspects and examples of such service or "drop" pits, and the hoisting mechanisms associated therewith are to be found in U.S. Pat. Nos.:
1,586,783- Coffey - June 1926;
1,632,256- Walter - June 1927;
1,706,211- Coffey - March 1929;
1,802,592- Christie - April 1931;
1,848,696- Christie - March 1932; and
3,055,310- Griffiths et al. - September 1962.
The use of such drop pits and associated facilities has more recently been complicated by the adoption of trains of semi-permanently, close coupled railway cars in multi-car packs, the disconnection of which is both labour intensive, time consuming and dangerous.
U.S. Pat. No. 4,295,427 shows a plant for refurbishing the trucks of railway car running gear, and includes a lateral transfer line along which the defective trucks and associated replacement trucks travel.